Method for producing elastic yarns and fabrics



United States Patent fiice 'sassari Patented June 20, 1967 3,325,876 METHD FOR PRODUCING ELASTC YARNS AND FABRECS Salim Meir Ibrahim, Wilmington, Del., assigner to E. l.

du Pont de Nemours and Company, Wiimington, Del.,

a corporation of Delaware Filed Aug. 5, 1.964, Ser. No. 387,713 6 Claims. (Cl. 28-72) This invention relates to a process for preparing elastic yarns and fabrics and more particularly to a process for preparing high-stretch elastic fabrics from yarns spun on a woolen system.

The manufacture `of elastic yarns from blends compr-ising a minor proportion of elastic staple fibers and a major proportion of inelastic staple fibers is described in U.S. Patent 3,007,227. Based upon this reference, yarns with desirably high levels of stretch and recovery can be readily produced on spinning frames of the kind commonly used in the cotton, modified cotton, or worsted systems of spinning. However, despite numerous attempts, it has not yet been possible to produce good high-stretch, high-recovery yarns from such blends on the woolen system. Even when blends containing a substantial percentage of elastic fibers are used, the resulting yarns have essentially no elasticity but beh-ave in a manner characteristic of yarns made only of inelastic fibers. Consequently, it has not been possible to employ the fiber blend technology to impart to the kinds of fabrics commonly made from woolen-spun yarns the kind of stretch characteristics that have become of increasing commercial importance.

The inability to produce high-stretch yarns on the woolen system has now been theorized to reside in the nature of the woolen spinning process, which is thought to be inherently incompatible with the requirements for producing high-stretch yarns. To impart characteristics of high-stretch and high-recovery to yarns made from blends of elastic and inelastic staple fibers, it is first necessary to y stretch the elastic fibers during spinning and then to lock them in the stretched state by the binding action of twist land by the frictional restraint of the inelastic fibers present in the yarn structure. These requirements are readily 'lmet vin the cotton and worsted systems of spinning. First, "these systems commonly employ relatively high drafts in excess of `6 times, adequate to stretch the elastic fibers in the blend the amount necessary to impart high-stretch `characteristics to the final yarn. Second, imparting and maintaining the desired stretch is assisted and close control of the fibers in the drafting zone is achieved by the plurality of rollers or the combination of rollers and aprons that conventionally comprise the drafting elements .in cotton and worsted spinning frames. Finally, the relatively high twist usually imparted to the yarn in cotton and worsted spinning assists in maintaining the elastic fibers in the stretched condition. l The reverse of these conditions obtains on woolen spinning ramesJFirSt, relatively low draft levels of less than 2 times arc commonly employed, this amount of draft being inadequate to stretch the elastic fibers in the blend sufficiently to impart high-stretch characteristics to the yarn. Second, woolen spinning frames do not have positive draft controls, such as rollers and aprons, but rely on false twist to control draft. Finally, woolen-spun yarns are customarily loosely twisted structures. Because of the low twist in the yarn structure and the lack of positive draft control in spinning, it is difficult to maintain even the small amount of stretch that may have been imparted to the elastic fibers in the blend, and the resulting yarns will have little or no stretch characteristics.

lt is, therefore, an object of this invention to provide A an -improved method for preparing high-stretch, high-recovery yarns from a blend of a minor proportion of elastic staple fibers and a major proportion of elastic fibers. It 1s another object of this invention to provide a method for preparing high-stretch elastic fabrics from yarns spun op a woolen system. Other objects will appear hereina ter.

The objects of this invention are achieved by a method which comprises, in general, stretching the elastic fibers a predetermined amount less than the breaking elongation, heat-setting the elastic fibers in the extended state, blending the heat-set elastic fibers with inelastic fibers, process-ing to yarns on the woolen system by procedures commonly employed in that system, and finally exposing the yarns (either before or after they have been formed into fabric) to a treatment which will release or unlock them from the heat-set condition and permit the elastic fibers to contract to impart stretch to the composite yarns. Both the elastic land inelastic fibers will be cut to lengths suitable for processing on woolen system equipment. In a preferred embodiment, the elastic fibers are heat-set in the form of tow before they are cut to staple lengths.

By the term elastic fibers, it is meant synthetic and natural fibers having a high breaking elongation, e.g., or more l'and preferably 500% to 800%, and a low elastic or initial modulus, e.g., less than one gram per denier, preferably 0.08 gram per denier or lower, and exhibit a quick and substantially complete recovery from stretching to an amount less than their breaking elongation, e.g., have a tensile recovery of about 90% or more and a stress decay of less than `about 20%.

By the term inelastic fibers it is meant those natural and synthetic fibers which generally have a breaking elongation of less than about 100% and, as compared to the elastic fibers, have a relatively high elastic or initial modulus, e.g., from 4 to 100 gra-ms per denier or greater.

In order to facilitate an understanding of this invention, reference may be had to the accompanying drawing which represents a schematic flow chart of the steps util-ized to form the high-stretch, high-recovery yarns.

As shown in the schematic, the elastic fibers are first stretched a predetermined amount less than their breaking elongation. It is preferred that the elastic fibers be extended from about 2.0 to about 6.5 times their relaxed length. While the elastic fibers are maintained in their extended condition, theyare heat-set in accordance with the general procedures outlined in Canadian Patent 621,- 569. The heat-setting treatment should be of a relatively mild order such that the elastic fibers are heat-set temporarily in their elongated condition. The treatment should not be so severe as to permanently stabilize the elastic fibers. Mild heat-setting treatments, e.g., treatment in steam at low pressure, in dry heat at C., or in boiling water, initially stabilize the elastic fibers but permit retraction of from 30% to 60% (based upon the extended length) when the fibers are subsequently exposed to a relaxing or unlocking treatment. Heat-setting conditions can be selected as desired to provide the balance between elasticity and retractive force in the final fabric.

After the heat-setting treatment (or other heat-setting and cutting if heat-setting has been carried out on the tow), a minor proportion of the elastic staple fibers are blended with a major proportion of the inelastic staple fibers on any suitable equipment. For woolen system processing, this will commonly be a woolen system blender, but the exact method and equipment used are not critical in the practice of this invention so long as thorough blending is achieved. The -blended fibers are then proessed on a woolen system card and a woolen system spinning frame. Because the elastic fibers comprise a minor proportion of the blend by weight, the carding and spinning operations can be conducted by the procedures commonly employed for totally inelastic fibers. Details of the carding and spinning operations, e.g., machine settings and speeds, size of roping, and the like, are not critical, but will be governed by the count desired in the final yarn.

After spinning, the yarn may be treated to unlock the elastic fibers. Preferably, however, the yarn is first made into fabric by knitting, weaving or other means, and the unlocking treatment is then carried out on the fabric to impart high-stretch characteristics to it. Fabric production is facilitated in this way because the yarns containing heat-set elastic fibers canV be handled in the same manner as totally inelastic yarns, thus minimizing problems commonly encountered in fabricating elastic yarns, such as control of tension and stretch. Stretch characteristics are then imparted to the fabric by exposure to treatment to unlock the heat-set elastic fibers. Because of the mild heat-setting conditions used, such a treatment may consist of boiling the fabric or exposing it brieiiy to atmospheric steam, or the treatment may be incorporated in such fabric finishing processes as scouring and dyeing.

The composite yarns made on the woolen spinning system according to the process of this invention may be combined with other yarns before being made into fabric, if desired. For example, they may be plied or twisted with inelastic yarns or helically wrapped with inelastic yarns, or they may be used as the core element in corn- Y bination with a roving of inelastic fibers in any of various methods of producing so-called core-spun yarns. It is preferred to have the proportion of elastic fibers to be in the range of from about 2% to about 50%. It is to be understood,however, that as little as about 1% of the total weight may be provided by the elastic fibers.

The invention is further illustrated by the examples that follow, wherein all parts are by weight unless otherwise specified.

Example I A tow of spandex fibers of 6 denier per filament is prepared as described in Example I of U.S. Patent 3,077,- 006. The spandex tow thus formed is extended at room temperature to four times its relaxed length, wound on dye tubes, and exposed for two minutes to dry heat at 160 C. After heat-setting in this manner, the tow is cooled and cut to staple fibers of three-inch length. These fibers are blended with a commercially available acrylonitrile polymer fiber of 3 denier per filament and 21/2 -inch length. The composition of the blend is 93% acrylonitrile polymer fibers and 7% spandex fibers. The blend is then processed on a woolen card and a woolen spinning frame by the procedures commonly used for acrylonitrile polymer fibers. A 3.0 wool run yarn is produced with a twist of t.p.i. Z. A sample of this yarn in skein form is relaxed by exposure to atmospheric steam for two minutes. After relaxation, the sampleis found to have a stretch of Mens socks are knit from the unrelaxed yarn on an 84-needle Komet machine in a rib stitch. The socks are relaxed by a boil-off for l5 minutes in a detergent bath. The feet of the relaxed socks are found to have a lengthwise stretch of about 10%.

By comparison, other yarns are prepared from the same starting materials but not by the process of this invention. The spandex tow is cut to 3inch lengths while in the relaxed condition, that is, without extension and without heat-setting. Carding and spinning are carried out as before. After relaxation in atmospheric steam for two minutes, the yarn is found to have essentially no stretch, as though it were made entirely of inelastic fibers. Socks are knit and finished from this yarn in the same manner as before. The feet of the relaxed socks are found to have a lengthwise stretch of 5%, which is essentially what would be obtained from a regular knit structure that contained no elastic fibers.

Example II Polytetramethylene ether glycol having a molecular n.weight of about 1000 (3000 parts) is mixed with 1500 (N,N-diethyl-beta-aminoethyl methacrylate) in dimethylf formarnide, such that the final mixture contains 5% of each additive based on the polyurethane.

This solution is then extruded through a 960-hole spinneret with an orice diameter of 0.0025 inch into an aqueous bath containing 45% dimethylacetamide and 7 to 12% talc, and maintained at about 65 C. The 4,200 denier tow thus formed is removed at about -40 to 50 yards per minute and passed through a Water `bath maintained at about 35 C. until the filaments contain lless than 0.5% dimethylacetamide. After application of a talcy finish, the t-ow is dried in a relaxed condition for three hours at 104 C. and then heated for 45 minutes at 140 C. The spandex tow thus produced has an individual filament denier of 4.3 and total tow denier of approximately 4,200.

Thespandex tow thus prepared is extended at room temperature to four times its relaxed length, heat-set in water at C. for 1l seconds, and cooled. The heatset tow is cut to 3inch lengths and blended with the acrylonitrile polymer staple fiber of Example I. The blend composition is 93% acrylonitrile polymer fibers and 7% spandex fibers. The blend is processed on a woolen card and a woolen spinning frame to make a 2.2 wool run yarn wi-th a twist of 4.5 t.p.i. Z. Processing procedures are those commonly used for acrylic fi-bers on the woolen system. A sample of this yarn relaxed in skein form as in Example has a stretch of 56% .after relaxation. Socks are knit from the unrelaxed yarn as in Example I. After relaxation as in Example I, the feet of the socks have a lengthwise stretch of 40%.

It will be apparent to those skilled in the art that any of a great number of elastic and inelastic natural and synthetic fibers may be substituted for those specifically disclosed in the foregoing examples. Among the many inelastic fibers are those prepared from the synthetic fiber-forming materials such as polyesters, acrylic polymers and copolymers, vinyl polymers, polyamides, polyhydrocarbons, cellulose and cellulose derivatives, or from any natural fibers, such as cotton, wool, silk or a blend of two or more inelastic fibers.v

A particularly suitable class of elastic fibers for use in this invention are the spandex fibers. Among the segmented polyurethanes of the spandex type are those described in several patents, among which are U.S. Patents 2,929,800, 2,929,801, 2,929,802, 2,929,804, 2,953,839, 2,957,852 and 3,097,192. As described in the aforementicned patents, these spandex fibers have elongations greater than tensile recovery of 90% and a stress decay of less than about 20%. Other suitable elastic fibers are described on columns 8 and 9 of U.S. Patent 3,077,006.

The above examples clearly illustrate that it is possible by the process of this invention to produce high-stretch yarns on the woolen system from a blend of elastic and inelastic staple fibers without need of special draft controls for the elastic fibers, and that particularly desirable results are achieved when spandex fibers of preferred.

composition are used.

The process -of this invention can be employed whereever it is desired to produce elastic yarns for the manufacture of woven, knitted and non-woven fabrics having a relatively high degree of elasticity. Examples of such uses are universal fitting apparel (socks, polo shirts,

underwear, bathing suits, gloves, elastic cuffs, sweaters, waistbands, suits, coats, dresses, skirts, action sportswear, leotard-type outer wear, and accessories such as tapes, webbings and other woven, non-woven or knit apparel fabrics), household products (form-fitting upholstery, Slipcovers, sheets, carpets, mattress coverings and narrow tapes and webbings for a wide variety of uses), industrial products (transportation upholstery, woven and nonwoven felts, tapes and webbings for varied applications), and medical products (surgical bandages, supports, elastic dressings, surgical stockings, and splint tapes). In addition, high stretch, moderate recovery fabrics can be made suitable for use in outer apparel (sweaters, knit jersey and woven, knit or non-woven suitings and dress goods), household items (rugs, carpets and upholstery), and industrial products (woven, non-woven and knit compression or impact-bearing structures). Illustrations of various specific products are shoe laces, shoe liner fabric, shoe upper fabrics, house slippers, skin diving suits, snow suits, ski pants, football pants, slacks, fiannels, sport shirts, bulky knit sweaters, blankets, swimming pool covers, toupee bases, belts, Suspenders, garters, watch bands, ropes, elastic sewing thread, shock cords, bookcover jackets, bookbinding cloth, synthetic paper, elastomer-coated fabrics, and super-dense felts, such as papermakers felts.

Fabrics made by this invention may be given the customary -finishing treatments where necessary or desired, such as scouring, washing, drying, pressing, dyeing and softening.

As many widely different embodiments of this invention may `be made without departing from the spirit and scope thereof, it is to be understood that this invention is not to be limited t-o the specific embodiments thereof except as defined in the appended claims.

What is claimed is:

1. The method of producing high-stretch, highrecovery yarns on the woolen system from a minor proportion of elastic fibers and a major proportion of inelastic fibers which comprises stretching said elastic fibers a predetermined amount less than the breaking elongation, temporarily heat-setting said elastic fibers in the stretched condition, blending the heat-set elastic fibers with said inelastic fibers, spinning the blend into yarn on a conventional woolen system utilizing draft levels 0f less than 2 times, including false twisting without positive draft controls to control draft and the loosely twisted fiber structures, and thereafter treating the formed yarn to release said temporary heat-setting and permitting said elastic fibers to retract to impart stretch to said formed yarn.

2. The method of producing high-stretch, high-recovery fabrics from a minor proportion of elastic fibers and a major proportion of inelastic fibers which comprises stretching said elastic fibers a predetermined amount less than the breaking elongation, temporarily heatsetting said elastic fibers in the stretched condition, blending the heat-set elastic fibers with said inelastic fibers,

spinning the blend into yarn on a conventional woolen system utilizing draft levels of less than 2 times, including false twisting without positive draft controls to control draft and the loosely twisted fiber structures, further processing the blend to form a fabric, and thereafter treating the formed fabric to release said temporary heatsetting and permitting said elastic fibers to retract to impart stretch to said formed fabric.

3. The method of claim 1 wherein said elastic fibers are stretched an amount from about 2.0 to 6.5 times their relaxed length.

4. The method of claim 2 wherein said elastic fibers are stretched an amount from about 2.0 to 6.5 times their relaxed length.

5. The method of producing high-stretch, high-recovery yarns on the woolen system from a minor proportion of about 2% to about 50% by weight of elastic fibers and a major proportion of inelastic fibers which comprises stretching said elastic fibers a predetermined amount less than the breaking elongation, said amount being from about 2.0 to 6.5 times their relaxed length, temporarily heat-setting said elastic fibers in the stretched condition, blending the heat-set elastic fibers With said inelastic fibers, spinning the blend into yarn on a conventional woolen system utilizing draft levels of less than 2 times, including false twisting without positive draft `controls to control draft and the loosely twisted fiber structures, and thereafter treating the formed yarn to release said temporary heat-setting and permitting said elastic fibers to retract to impart stretch to said formed yarn.

6. The method 0f producing high-stretch, high-recovery fabrics from a minor proportion of about 2% to about 50% by weight of elastic fibers and a major proportion of inelastic fibers which comprises stretching said elastic fibers a predetermined amount less than the fbreaking elongation, said amount being from about 2.0 to 6.5 times their relaxed length, temporarily heat-setting said elastic fibers in the stretched condition, blending the heatset elastic fibers with said inelastic fibers, spinning the blend into yarn on a conventional woolen system utilizing draft levels of less than 2 times, including false twisting without positive draft controls to contr-ol draft and the loosely twisted fiber structures, further processing the blend to form a fabric, and thereafter treating the formed fabric to release said temporary heat-setting and permitting said elastic fibers to retract to impart stretch to said formed fabric.

References Cited UNITED STATES PATENTS 3,007,227 11/1961 Moler 57--140 3,077,006 2/1963 Ibrahim 19-.48 3,120,095 2/ 1964 Guthrie et al.

FOREIGN PATENTS 916,287 l/l963 Great Britain.

ROBERT R. MACKEY, Primary Examiner. 

1. THE METHOD OF PRODUCING HIGH-STRETCH, HIGHRECOVERY YARNS ON THE WOOLEN SYSTEM FROM A MINOR PROPORTION OF ELASTIC FIBERS AND A MAJOR PROPORTION OF INELASTIC FIBERS WHICH COMPRISES STRETCHING SAID ELASTIC FIBERS A PREDETERMINED AMOUNT LESS THAN THE BREAKING ELONGATION, TEMPORARILY HEAT-SETTING SAID ELASTIC FIBERS IN THE STRETCHED CONDITION, BLENDING THE HEAT-SET ELASTIC FIBERS WITH SAID INELASTIC FIBERS, SPINNING THE BLEND INTO YARN ON A CONVENTIONAL WOOLEN SYSTEM UTILIZING DRAFT LEVELS OF LESS THAN 2 TIMES, INCLUDING FALSE TWISTING WITHOUT POSITIVE DRAFT CONTROLS TO CONTROL DRAFT AND THE LOOSELY TWISTED FIBER STRUCTURES, AND THEREAFTER TREATING THE FORMED YARN TO REALES SAID TEMPORARY HEAT-SETTING AND PERMITTING SAID ELASTIC FIBERS TO RETRACT TO IMPART STRETCH TO SAID FORMED YARN.
 2. THE METHOD OF PRODUCING HIGH-STRETCH, HIGH-RECOVERY FABRICS FROM A MINOR PROPORTION OF ELASTIC FIBERS AND A MAJOR PROPORTION OF INELASTIC FIBERS WHICH COMPRISES STRETCHING SAID ELASTIC FIBERS A PREDETERMINED AMOUNT LESS THAN THE BREAKING ELONGATION, TEMPORARILY HEATSETTING SAID ELASTIC FIBERS IN THE STRETCHED CONDITION, BLENDING THE HEAT-SET ELASTIC FIBERS WITH SAID INELASTIC FIBERS, SPINNING THE BLEND INTO YARN ON A CONVENTIONAL WOOLEN SYSTEM UTILIZING DRAFT LEVELS OF LESS THAN 2 TIMES, INCLUDING FALSE TWISTING WITHOUT POSITIVE DRAFT CONTROLS TO CONTROL DRAFT AND THE LOOSELY TWISTED FIBER STRUCTURES, FURTHER PROCESSING THE BLEND TO FORM A FABRIC, AND THEREAFTER TREATING THE FORMED FABRIC TO RELEASE SAID TEMPORARY HEATSETTING AND PERMITTING SAID ELASTIC FIBERS TO RETRACT TO IMPART STRETCH TO SAID FORMED FABRIC. 